Chow, who cried inside the court room on hearing the sentence, had pleaded guilty to incitement and participation in an unlawful protest, while Lam pleaded guilty to incitement.
Wong, 24, and Lam, 26, have previously been jailed over charges related to their activism. "(Chow) took an active part at the assembly, remaining at the (police headquarters) for about 15 hours, chanting slogans continuously throughout and assisting (Wong) by his side".
The crackdown has prompted accusations Beijing is violating the autonomy it promised when the former British colony was returned to China in 1997. According to the court ruling, Wong was sentenced to nine months for the incitement charge, more than the 7.5-month sentence issued to Chow, because Wong "took a more active role" that day.
Maria Adebahr, a spokeswoman for Germany's foreign ministry, told reporters in Berlin that the sentences are "another building block in a series of worrisome developments that we have seen in connection with human and civil rights in Hong Kong during the a year ago".
They also jailed Wong's colleagues Agnes Chow and Ivan Lam for 10 and seven months, respectively.
Hong Kong media tycoon and pro-democracy activist Jimmy Lai was denied bail on Thursday on a charge of fraud related to the lease of a building that houses his Apple Daily, an anti-government tabloid.
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Jimmy Lai of Next Digital, which publishes the Apple Daily newspaper, was among 10 people arrested August 10 on what police said was suspicion of violating a national security law and collusion with a foreign country.
IPAC added that the sentencing "has made a mockery of the rule of law in the city" and demonstrated the Chinese regime's erosion of freedoms that were guaranteed in the city's mini-constitution, Hong Kong Basic Law, and Sino-British Joint Declaration. But for Chow, this will be her first time in prison, sentenced on the eve of her 24th birthday.
"The days ahead will be tough but we will hang in there", Wong shouted as he was led away.
Hong Kong pro-democracy leaders were arrested and sentenced to prison on Wednesday following their involvement in a series of protests created in resistance to the Chinese Communist Party's tightening control of the territory.
All three organized successful rallies in 2012 against plans to make Hong Kong's education system more "patriotic".
The decision effectively sidelines one of the most prominent critics of the Hong Kong government and its backers in Beijing.
"When Hong Kong police picked him up Wednesday on dubious fraud charges, China was sending a clear message: If you oppose us anywhere in the world, we will crush you".
He has been convicted four times for pro-democracy protests or rallies against various government proposals.